Processes for solidifying a coal ash with a hydration reaction by adding an additive such as lime (slaked lime, quick lime), cement, slag or gypsum are well known, and the hydrating reactivity of the coal ash has been known to correlate with its CaO quantity, basicity (CaO/SiO2) and the like to some extent (for example, Patent Document 1, claim 1). However, it is difficult to estimate the hydrating reactivity of the coal ash with some accuracy, based merely on the CaO quantity or basicity.
In addition, when a kneaded material is obtained by adding an additive and water for kneading to a coal ash, it is desired to obtain the kneaded material in the funicular state constantly. In a known process to meet this end, a small amount of water is added first, and the extent of rise in the agitator motive power of the kneading machine resulting from the addition is used for estimating the finally needed amount of water for kneading, whereby the water for kneading is added in an amount based on the estimated amount that suggests the deficient amount to be added (for example, Patent Document 1, claims 6 and 7). However, according to this process, the estimated amount of water to be charged may vary fairly broadly, and thus more accurate process for determining the estimated amount of water for kneading has been desired.
Furthermore, for obtaining molded products of a kneaded material, as is employed in the case of producing concrete blocks, known methods may involve: a process in which powder cement, aggregate and the like are kneaded with water to form a kneaded material in the pendular state, which is molded under a low pressure and vibration, and then subjected to demolding immediately; or a process in which ready-mixed concrete in the capillary state is solidified by vibration molding, and then subjected to demolding. However, since the hydration reaction does not proceed enough with kneaded material in the pendular state, elution of a heavy metal or the like may occur, while handling characteristics may be inferior in the case of the capillary state, thereby leading to disadvantages of deteriorated strength of the granular solid material.
Additionally, in molding after the kneading, a low-pressure vibration molding machine has been employed conventionally. Although this low-pressure vibration molding machine utilizes a loading plate for pressurization from above the mold form, the kneaded material may adhere to the loading plate depending on the amount of the water for kneading, and thus problems may be posed in that operation of the production apparatus can be hampered.
Moreover, in crushing the solid material after curing, a crushing machine is typically used to effect crushing. However, these processes are disadvantageous in that a granular solid material having a predetermined particle size cannot be obtained constantly to meet each application.    Patent Document 1: JP-A No. 2002-211968 (claims 1, 6 and 7)